Electric discharge apparatus



May 15, 1934. H, FRONDT 1,959,201

ELECTRIC DISCHARGE APPARATUS Filed March 22, 1932 Fig.1.

Fig.2.

Inventor": Hermann Fm'jndt,

+ w His Attorney.

Patented May 15, 1934 UNITED STATES PATENT OFFICE ELECTRIC DISCHARGE APPARATUS poration of New York Application March 22, 1932, Serial No. 600,553 In Germany March 25, 1931 Claims.

The present invention relates to electric discharge apparatus, more particularly to gas or vapor devices which operate with an arc-like discharge. An object of the invention is to provide automatic ignition and starting of the device in response to changes of temperature of the discharge space or of the envelope of the device.

It is known that in gas or vapor discharge devices, such as mercury-arc rectifiers, which operatein places of relatively low ambient temperature, the starting of the arc may be difiicult; moreover, during the interval before ignition, excess potentials are built up which may give rise to reverse arcing. I

In order to facilitate starting under these conditions, there has been provided in the interior, also on the exterior of the envelope, a heating member which serves to raise the temperature of the vapor or gas to the proper value before the tube is energized. The heater has usually been connected to and disconnected from its source of energy, when necessary, by hand and the effectiveness of the heating element has been dependent entirely upon manual control. The present invention replaces the prior manual control by an automatic arrangement which offers the advantages of the heating device, even in unattended apparatus.

My invention contemplates the use of an automatic system for switching the heater in and out of service when desired and depending upon the temperature of the envelope and contained gas r or vapor. When the heater is switched out, the improved arrangement is such that electrical energy is immediately transmitted to the tube so that the latter automatically takes the load as soon as the temperature of the vapor or gas has reached a satisfactory condition.

In accordance with the invention, a heat-sensitive device is employed in addition to the heater and is arranged in heat-responsive relation to the discharge so as automatically to control the starting of the various operations. My invention also contemplates the automatic starting of a cooling device when the tube is energized in response to the operation of the heat-sensitive member. Other objects and features will be apparent as the specification is perused in connection with the accompanying drawing, in which Fig. 1 is a diagrammatic View of the improved system as applied to a mercury arc rectifier of standard design, and Fig. 2 shows the application of the invention to a rectifier containing a thermionic cathode.

In Fig. 1, numeral 1 designates the envelope of an electric discharge tube containing a. mercury pool cathode 2, a pair of main electrodes 3, an ignition anode 4 and a pair of exciting anodes 5. The anode 4 is adapted to move longitudinally in the direction of the main axis of the tube. There are arranged in the vicinity of the envelope, as close as possible to the glass, a heater 6 of ordinary type and a heat-responsive device '7 consisting preferably of a thermostatic relay. A coil 8 surrounds the member 4 for the purpose of dipping the member in the mercury, as will be explained hereinafter. The coil 8 is shown for convenience as being removed from the electrode 4 and may be positioned within the envelope so as closely to embrace the electrode but preferably is wound about the glass on the exterior. There is a blower or fan 9 positioned near the envelope, preferably at the upper or hottest portion to cool the rectifier during operation. The fan is exemplified as a three-phase device of standard design.

The main circuit of the rectifier, i. e., between the respective anodes 3 and the cathode 2, is energized by a transformer 10 connected to alternating current mains 11. The direct current output of the rectifier is taken from the cathode 2 and mid-tap of the main transformer secondary. There is the usual transformer 12 for the exciting and igniting electrodes, the secondary winding 13 being connected between the exciting electrodes 5 by conductors 14, a mid-tap and conductor 15 being also joined to the cathode. Each of the conductors 14, 15 includes a choke coil 16 for holding the arc, as is well understood in the art. One end of the secondary 1'7 is connected directly to the cathode 2 through conductors 18, 19 and a portion of conductor 15, the other end of the secondary being connected to the igniting electrode 4 through the conductor 20, a switching mechanism and a resistance 21. This last-mentioned circuit is also connected to the coil 8 so that the latter is in shunt to the path between the igniting electrode 4 and the cathode 2.

The primary winding of the transformer 12 is energized from a suitable alternating current supply, exemplified as part of a three-phase system 22, provided with a triple-bladed switch 23 for closing the circuit. This three-phase supply also energizes the fan 9 when the various switching mechanisms have operated.

The mid-tap conductor 15 has a coil or electromagnet 24 in series therewith, inserted preferably between the choke 16 and the cathode 2. This coil is energized by current flowing through the respective exciting electrodes and the cathode. There is a coil 25 arranged in series with a current-limiting resistance 26, and connected across a pair of conductors 14, 15. This coil is operated from the voltage derived from onehalf of the secondary 13.

The coil 24 is provided with a movable core biased at the lower end as shown by a spring 27 and carrying armatures 28, 29 at the respective ends. The armature 28 cooperates with a pair of contacts 30 to make and break the igniting anode circuit, while the other armature 29 cotil operates with contacts 31 to open and close the circuit containing coil 25.

The coil 25 has a long movable core which contains, intermediate its length, a tension spring 32, and at the upper end, as shown, is secured to a dashpot 33 of any suitable design; The core carries two armatures 34 and 35 which cooperate respectively with contacts 38 and 39, also an armature 36 which cooperates with contacts 40 and 41., and an armature 37 which cooperates with contacts 42 and 43. These contacts are arranged inthe various circuits. The contacts '38 associated with armature 34 'form part of the main alternating current supply line 11, while the contacts 39 cooperating with the armature 35 are connected in the circuit containing contacts 30 and the igniting electrode 4. The contacts 40 and 41, also 42 and 43, constitute front and back contacts for the respective armatures 36, 37, the respective front or upper contacts as shown being connected in each side of the heater circuit, and the respective rear or lower contacts as shown being connected in the blower or fan circuit. It is apparent that the function of the spring .32 and dashpot 33 is to permit the armature 34 to close the contacts 38 at a time considerably later than the closing of the other contacts by their respective armatures when the core moves downward.

The thermostatic relay '7 consists preferably of a bimetallic strip, bent into U-shape and provided with a contact 44. The strip and contact member areconnected in shunt to the coil 25, hence across the potential operated line 14, 15.

The operation of the sytem will be clear in view of the followingexplanation. The switch 23 is first closed, thereby causing the energization of transformer 12 from one of the phases of the three-phase system 22. The potential coil 25 is also energized from the right-hand half of the secondary winding 13 and causes the core to move upwardly, carrying the armatures 36, .37 to their upperposition and completing the circuit ofthe heater 6 across the contacts 40 and 42. These contacts are connected to .a phase of the three-phase system, and consequently the heater becomes energized. As a result of the movement of the core, the armature 35 moves away from contacts 39, thereby opening all of the circuits which terminate at the secondary 17. Hence, there is no current flowing in coil 8 which ac'tuates the electrode 4, and for well-known reasons there can be no current flowing through the exciting electrodes 5. It will also be noted that armature 34 is moved upwardly away from contacts 38 so that the main circuit 11 is broken and no alternating current is supplied to the anode-cathode circuit of the rectifier. V

Asstated hereinbefore, the heater '6 is energized during this time and continues to heat the en- "ve'lope '1, also the contained mercury. When the envelope has 'reacheda predetermined temperature, suitable for taking over the direct current load, the thermostatic *relay 7 closes the contact 44 and completes the circuit 45 which is in shunt to the coil 25. The closing of this circuit causes coil 25 to be ole-energized which thereupon allows its core to move downwardly, carrying the armatures immediately to their lower positions with the exception of armaturre 34. The armature 34 tends to move'downwa-rdly with the other armatur'es, but due to the'delaying action of the dashpot 33 and the presence of the spring 32 is I precluded from immediately following them."

Consequently, the alternating current circuit through conductors 11 remains temporarily broken, at least until several. other operations have taken place as will be described presently.

The armature 35, upon moving, closes a circuit through armature 28 and resistance 21 to the coil 8 back to the secondary 17. The resistance 21 is employed for the purpose of limiting the current through coil 8 during this period. When the latter is energized, the resulting electromagnetic field causes the electrode 4 to .be dipped into the mercury cathode. As soon as the electrode 4 touches the mercury, it is apparent that the coil 8 is automatically short circuited, hence de-energized, so that the electrode 4 is permitted to move upwardly to its initial position. This upward movement may be obtained by any suitable form of mechanical or electrical bias.

On the return of the igniting anode to its initial position, exciting arcs are caused to form between the cathode 2 and the respective electrodes .5. There is thus provided a closed exciting circuit from the winding 13 through one of the choke coils '16, one of the exciting electrodes 5, the cathode 2, the coil '24, another of the choke coils 16, back to the mid-tap of the V exciting winding 13.

If the ignition does not take place in the rectifier immediately after the dropping of the arma ture 35, the operation .of the igniting anode 4 is repeated until the ignition takes place, or the thermostatic relay? has, on account of the failure.

of heat radiation, opened its contact 44, thereby again permitting the relay 25 and the .associated heater 6 to -be energized.

As stated hereinbeiore, the coil 24 becomes energized when the exciting arcs arefforme'd, and hence its core moves upwardly against the tension spring 27 and causes the armature 28 to open its contacts 30 and the armature '29, to

break the circuit through coil '25 at the contacts 31. It will be understood that coil 25 had previously been short circuited by the operation of the thermostatic relay so that the opening of contacts 31 simply serves to remove this short circuit from the coil and also from "the pair of conductors 14, 15, which the. short circuit efiectively spans, as will be seen from the drawing.

Armatures 36,. 3'7, in moving,jbreak the heater circuit and connect the fan' or blower '9 to the ,2

V The armature 34 which has been slowly moving toward its lower position durthree-phase line;

'23 and'the applicationof alternating current to the'rectifier may be accurately controlled by-t-he design and characteristics of the various circuits, also by the adjustment of the dashpot 33.

The invention is not limited to rectifiers of the mercury-arc type but applies also to other forms of electrical discharge devices. Thus in Fig. 2, I have shown an application of the improved system to a rectifier containing a filamentary cathode and which may or may not be of the arc or glow discharge type. In this modification, the thermostatic relay is shown as being positioned within the envelope where it will respond more accurately to changes of temperature within the tube than in the case of a position external to the tube.

The arrangement of Fig. 2 is such that when the switch 50 is closed, the transformer 51 is energized from the alternating current mains 52 and heats directly or indirectly the hot cathode 53, shown as a filament, through the secondary winding of the transformer. The heating current energizes relay 54, the core of which moves downwardly against the tension spring 64 to close the circuit containing contacts 55, the coil 56 and a current-limiting resistance 57. The coil 56 is connected across the secondary of the transformer 51 so that it now becomes energized and forces its core upwardly against the bias spring 58 to close the heater circuit 59 at contacts 60. The heater then proceeds to warm up the envelope as in the other figure, but after the operation of thermostatic relay 61 as a result of the increase in temperature there is no auxiliary discharge, i. e., ignition or excitation. The main discharge is directly initiated by the closure of the main energizing circuit through the primary winding 61', contacts 62, now closed by the armature of coil 54, and contacts 63 closed by the armature of coil 56 when the latter is short circuited by the operation of the thermostatic relay. If from any cause the heating current of the cathode is interruptedfor example in consequence of the fusing of the heating wire or filamentthe relay 54 returns to its upper or deenergized position and opens the main circuit at the contact 62, also the energizing circuit of the relay 56 so that the tube and the system are entirely de-energized except for the primary of transformer 51 and the fan 9.

For electrostatically controlled hot-cathode discharge apparatus containing a grid, in which case an auxiliary arc may be desirable, for example, for reducing the charging up of the glass walls, a switching arrangement similar to that shown in Fig. 1 may be employed in combination with the system shown in Fig. 2.

In addition to the switching arrangements shown in these two figures, other combinations of cooperating switches and apparatus may be included, as for example arrangements which cause the cooling fan to start only when the load exceeds a predetermined amount. Safety apparatus which indicates failures in the circuits or failure of the several devices to operate may also be included in the improved systems, as will readily occur to those skilled in the art.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an envelope containing a mercury cathode, an anode, igniting and exciting electrodes, means for heating the envelope, means for cooling the envelope, means including a single thermostatic relay and operating in response to the temperature of the envelope for de-energizing the heater and for simultaneously energizing the cooling means, also energizing the igniting and exciting electrodes, whereby the device is conditioned for the application of electrical energy to the cathode and anode.

2. In combination, an envelope containing a mercury cathode, an anode, igniting and exciting electrodes, means for heating said envelope, a source of electrical energy, means for connecting said source to the cathode and anode after the heater has conditioned the envelope to a predetermined temperature, said means including a single thermostatic relay which operates to cause the energization of the igniting and exciting electrodes, also the de-energization of the heater, finally causing said connection of the electrical energy source to the cathode and anode.

3. In combination, an electric discharge device comprising an envelope containing a mercury cathode and an anode, exciting and igniting electrodes, a source of electrical energy for said device, means for heating the device, and means including a single member responsive to the temperature of the device for de-energizing said heater and for energizing the igniting and exciting electrodes, said last-mentioned means also causing the application of the electrical energy to the device after a predetermined time delay.

4. In combination, an electric discharge device comprising an envelope containing a. mercury cathode and an anode, exciting and igniting electrodes, a source of electrical energy for said device, means for heating said device, and means including a single member responsive to the temperature of the device for de-energizing said heater and for energizing the igniting and exciting electrodes, finally causing the application of the electrical energy to said device, said application being delayed until after the igniting and exciting electrodes have been energized.

5. A system for automatically delaying the application of alternating current potential to a rectifier until the rectifier has reached a predetermined temperature, said system including a heater, a thermostatic relay which responds to the temperature of the rectifier, and a switching mechanism controlled by said relay for de-energizing the heater and for connecting a source of alternating current to the rectifier, said mechanism including a mechanical delay device which precludes the connecting of the source of alternating current to the rectifier until the rectifier has reached the predetermined temperature.

HERMANN FRCBNDT. 

